In a large random sample of undergraduate university students, we investigated whether sexual minority individuals (i.e., lesbian, gay, and bisexual individuals) experienced different rates of sexual violence victimization (including sexual assault and rape) and subsequent institutional betrayal compared to their heterosexual counterparts, and whether such differences may account for disparities in the psychological and physical health of sexual minorities compared to heterosexuals. In addition to differences in sexual assault victimization rates by gender and sexual orientation, we found differences in rates of institutional betrayal. When non-heterosexual women experienced sexual assault, they experienced a significantly higher rate of institutional betrayal compared to heterosexual women. Overall, greater institutional betrayal was associated with greater negative psychological and physical health outcomes in sexual minorities compared to heterosexual students. These findings reinforce the need for institutional reforms related to the climate and reporting of sexual violence on college campuses, and also identify sexual minority students as a population of particular risk for additional harm by their institutions when they need them most.